Porous inorganic oxide materials prepared by non-ionic surfactant templating route

Abstract

A method for the preparation of new quasi-crystalline, porous inorganic oxide materials possessing uniform framework-confined mesopores in the range 2.0-10.0 nm and large elementary particle size of more than 500.0 nm. The method uses an interaction between various nonionic polyethylene oxide based surfactants (N°) and neutral inorganic oxide precursors (I¤) at ambient reaction temperatures. The materials formed exhibit semi-ordered arrays of well defined pores owing to the specific mechanism of self-assembly, large pore wall thicknesses of at least 2.0 nm producing highly stable materials and large particle sizes incorporating large numbers of pores. This (N° I°) templating approach introduces several new concepts to mesostructure synthesis. The application of the low-cost, non-toxic and biodegradable surfactants and ambient reaction temperatures, introduces environmentally clean synthetic techniques to the formation of mesostructures. Recovery of the template can be achieved through solvent extraction where the solvent may be water or ethanol.

We claim: 
     
       1. A synthetic, semi-crystalline inorganic metal oxide composition having at least one resolved x-ray reflection corresponding to a lattice spacing of 3 to 10 nm, a framework wall thickness of at least about 2 nm, framework confined pores between about 2 and 10 nm, an elementary particle size greater than 500 nm, and a specific surface area of 300 to 1200 square meters per gram. 
     
     
       2. The composition of claim 1 having an X-ray diffraction pattern selected from the group consisting of FIGS. 3 and 5. 
     
     
       3. The composition of claim 1 having an N 2  adsorption-desorption isotherms and Horvath-Kawazoe pore size distribution selected from the group consisting of FIGS. 4 and 6. 
     
     
       4. The composition of claim 1 having an X-ray diffraction pattern as shown in FIG. 7. 
     
     
       5. The composition of claim 1 having N 2  adsorption-desorption isotherms and Horvath-Kawazoe pore size distribution as shown in FIG. 8. 
     
     
       6. A synthetic, semi-crystalline inorganic metal oxide composition having at least one resolved x-ray reflection corresponding to a lattice spacing of 3 to 10 nm, a framework wall thickness of at least about 2 nm, framework confined pores between about 2 and 10 nm, an elementary particle size greater than 500 nm, and a specific surface area of 300 to 1200 square meters per gram prepared by reacting a mixture of a non-ionic poly(alkylene oxide) derived surfactant as a template (N°) and a neutral inorganic metal oxide precursor (I°), followed by hydrolysis and crosslinking of the inorganic oxide precursor to provide the composition. 
     
     
       7. The composition of claim 6 wherein the template is removed from the composition. 
     
     
       8. The composition of claim 6 wherein the surfactant has a terminal hydroxyl group. 
     
     
       9. The composition of claim 6 which has the composition:   nR--EO/A.sub.x O.sub.Y     wherein R--EO is selected from the group consisting of nonionic alkyl polyethylene oxide, alkyl and aryl polyethylene oxide, and polyethylene oxide-polypropylene oxide-polyethylene oxide block copolymer molecules; A is a metal atom; O is oxygen and x and y are the molar stoichiometries of A, and O such that in the composition when calcined, n is about O, x is about 1, y is about 2.   
     
     
       10. The composition of claim 6 which has the composition:   nR--EO/A.sub.v B.sub.w Si.sub.x D.sub.y O.sub.z     wherein R--EO is selected from the group consisting of nonionic alkyl polyethylene oxide, alkyl and aryl polyethylene oxide and polyethylene oxide-polypropylene oxide-polyethylene oxide block co-polymer molecules; A is at least one optional trivalent element selected from the group consisting of Al, Ga and Fe; B is at least one optional tetravalent metallic element selected from the group consisting of Ge, Ti, V, Sb and Zr; Si is silicon; D is optional and is a pentavalent or hexavalent element selected from the group consisting of V, W and Mo; O is oxygen and v, w, x, y and z are the molar stoichiometries of A, B, Si, D and O respectively, wherein in the composition when calcined, n is about 0, ≦v≦2, 0≦w≦1, 0≦x≦1, 0≦y≦2 and 2≦z≦6.   
     
     
       11. The composition of claim 6 having X-ray diffraction patterns with at least one reflection corresponding to a lattice of between about 3 to 10 nm. 
     
     
       12. The composition of any one of claims 1 or which after calcination, has an N 2 , O 2  or Ar adsorption-desorption isotherm with a step at P/P O  between 0.2 and 0.6 and at least one hysteresis loop. 
     
     
       13. The composition of claim 12 wherein a ratio of textural to framework-confined mesoporosity as determined by the N 2 , O 2  or Ar adsorption isotherm, is about zero. 
     
     
       14. The composition of claim 13 the composition has a specific surface area between 500 and 1200 m 2  per gram. 
     
     
       15. The composition of claim 6 wherein a molar ratio of nonionic surfactant to inorganic oxide precursor in the reaction mixture is between 0.05 and 0.2. 
     
     
       16. The composition of claim 6 containing the template. 
     
     
       17. The composition of claim 6 in which the template has been removed by calcination. 
     
     
       18. The composition of claim 6 in which the template has been removed through solvent extraction. 
     
     
       19. The composition of claim 6 containing the template. 
     
     
       20. The composition of claim 10 in which the template has been removed by calcination. 
     
     
       21. The composition of claim 10 in which the template has been removed through solvent extraction. 
     
     
       22. The composition of any one of claims 1 or 6 in which at least one transition metal is dispersed or impregnated in the pores, selected from the group consisting of Ag, Au, Cu, Co, Cr, Ni, Fe, Ir, Mo, Pt, Pd, Sn, Ti, V, W, Zn and Zr. 
     
     
       23. The composition of any one of claims 1 or 6 containing transition metal substituted organic macrocycles in the pores. 
     
     
       24. The composition of claim 6 wherein the surfaces of the composition have been functionalized by an alkyl metal alkoxide precursor represented as M--R(OR).sub.χ-1, where M is the metal, x represents available bonding sites on M and where R is alkyl and OR is alkoxide. 
     
     
       25. The composition of any one of claims 6 or 10 wherein the surfaces of the composition upon removal of the template have been functionalized by substitution of the metal alkoxide precursor by a metal carboxylate precursor. 
     
     
       26. The composition of any one of claims 1 or 6 wherein the compositions have surfaces which have been functionalized by reaction of the composition upon removal of the template and calcination with reagents selected from the group consisting of chlorides, fluorides, sylisation and alkylation reagents. 
     
     
       27. The composition of claim 6 wherein the template (N°) is selected from the group consisting of primary, secondary and tertiary fatty alcohol poly(ethoxylates). 
     
     
       28. The composition of claim 6 wherein the nonionic template (N°) is an alkyl phenol poly-(ethoxylates). 
     
     
       29. The composition of claim 6 wherein the nonionic template (N°) is a fatty acid ethoxylate. 
     
     
       30. The composition of claim 6 wherein the nonionic template (N°) is a poly(ethylene oxide-propylene oxide) block co-polymer. 
     
     
       31. The composition of claim 6 wherein the template (N°) is selected from the group consisting of primary and secondary fatty amine poly(ethoxylate). 
     
     
       32. The composition of claim 6 wherein the template (N°) is a fatty acid poly(ethylene oxide-propylene oxide) block co-polymer. 
     
     
       33. The composition of claim 6 wherein the template (N°) is selected from the group consisting of fatty acid alkanolamides and ethoxylates. 
     
     
       34. The composition of claim 6 wherein the template (N°) is selected from the group consisting of sorbitan esters and sorbitan ethoxylates. 
     
     
       35. The composition of claim 6 wherein the template (N°) is a polyamine propoxylate ethoxylate. 
     
     
       36. A method for the preparation of a synthetic semi-crystalline inorganic oxide composition which comprises: (a) forming a solution by providing a mixture of (i) a neutral inorganic oxide precursor (I°) containing at least one element selected from the group consisting of di-, tri-, tetra-, penta- and hexavalent elements and mixture thereof; (ii) a non-ionic poly(alkylene oxide) surfactant (S°) as a template; and (iii) a hydrolyzing agent;   (b) mixing the solution to form a gel containing the composition;   (c) separating at least some of the hydrolyzing agent and the surfactant from the gel; and   (d) optionally calcining the composition.   
     
     
       37. The method of claim 36 wherein the gel is prepared by a random order of addition of the neutral template and neutral inorganic oxide precursor. 
     
     
       38. A method for the preparation of a synthetic, semi-crystalline inorganic oxide composition which comprises: (a) preparing a solution of a neutral inorganic oxide precursor (I°), containing at least one element selected from the group consisting of di-, tri-, tetra-, penta- and hexavalent elements and mixtures thereof with stirring and optionally aging the inorganic oxide precursor (I°) solution;   (b) preparing a homogeneous solution of a nonionic poly(alkylene oxide) surfactant (S°) as a template in a hydrolyzing agent, and optionally in a co-solvent, by stirring it at a temperature between about minus 20° and plus 100° C;   (c) mixing of the solutions of steps (a) and (b) at a temperature between about minus 20° and plus 100° C to form a gel which is aged for at least about 30 minutes to form the composition;   (d) separating at least some of the hydrolyzing agent and surfactant from the composition; and   (e) optionally calcining the composition.   
     
     
       39. The method of claim 38 wherein the neutral precursor is selected from the group consisting of a metal alkoxide, an inorganic complex, a colloidal inorganic oxide solution, an inorganic oxide sol and mixtures thereof. 
     
     
       40. The method of claim 38 wherein said inorganic oxide precursor solution is mixed without aging. 
     
     
       41. The method of claim 38 wherein the template is separated from the composition and as an additional step recycled after step (d). 
     
     
       42. The method of claim 41 wherein the template is separated by extraction with a solvent selected from the group consisting of a neutral organic solvent, water and mixtures thereof. 
     
     
       43. The method of claim 38 wherein in step (a) the solution is a gel with the stirring at a temperature of at least minus 20° C for at least 5 minutes. 
     
     
       44. The method of claim 38 wherein the composition is calcined at about 300° to 1000° C. for at least about 30 minutes. 
     
     
       45. A method for the preparation of a crystalline inorganic oxide composition which comprises: (a) preparing a homogeneous solution of nonionic poly(ethylene oxide) surfactant as a template (N°) in a lower alkyl alcohol solvent by mixing at ambient temperature;   (b) adding an inorganic metal precursor to the solution of step (a) at ambient temperature under stirring for at least 30 minutes to form a homogeneous solution;   (c) slowly adding a solution of a hydrolyzing agent to the homogeneous solution to form a gel as a first precipitate in the aqueous solution;   (d) aging of the first precipitate with stirring;   (e) redispersion of the first precipitate in a lower alkyl alcohol;   (f) aging the redispersion under stirring at ambient temperature for 16 to 48 hours to form a second precipitate;   (g) separating the aqueous solution, lower alkanol and at least some of the template from the second precipitate by washing once with ethanol; and   (h) drying the second precipitate in air at ambient temperature to form the composition.   
     
     
       46. The method of claim 45 wherein the calcining is by combustion in air. 
     
     
       47. The method of claim 45 wherein optionally heat treating the second precipitate to at least 373° K. in air for at least 16 hours. 
     
     
       48. The method of claim 45 wherein after step (h) the template is removed by solvent extraction. 
     
     
       49. The method of claim 45 wherein after step (h) the second precipitate is calcined between about 673° K. and 923° K. in air for at least 4 hours. 
     
     
       50. A method for the preparation of synthetic, semi-crystalline inorganic silicon dioxide composition which comprises: (a) preparing a homogeneous aqueous solution of a nonionic poly(ethylene oxide) derived surfactant template (N°) with mixing at ambient temperature;   (b) adding an inorganic silica precursor to the solution of step (a) at ambient temperature with stirring to form a solid, precipitate;   (c) aging of the precipitate with stirring at ambient temperature for between 16 and 48 hours;   (d) separating the aqueous solution and template from the precipitate followed by washing once with deionized water;   (e) drying the precipitated and separated precipitate in air at ambient temperature;   (f) heat treating the air dried precipitate in air at least 373° K. for at least 16 hours;   (g) optionally removing any remaining template by solvent extraction from the heat treated precipitate; and   (h) calcining the precipitate to remove any remaining template to cross-link the framework at between 673° K. and 923° K. in air for at least 4 hours to form the composition.   
     
     
       51. The method of claim 50 wherein the calcining is by combustion in air.